Time filter

Source Type

Wan L.,National Marine Environmental Forecasting Center | Bertino L.,Mohn Sverdrup Center | Zhu J.,CAS Institute of Atmospheric Physics
Journal of Atmospheric and Oceanic Technology | Year: 2010

The ensemble Kalman filter (EnKF) has proven its efficiency in strongly nonlinear dynamical systems but is demanding in its computing power requirements, which are typically about the same as those of the fourdimensional variational data assimilation (4DVAR) systems presently used in several weather forecasting centers. A simplified version of EnKF, the so-called ensemble optimal interpolation (EnOI), requires only a small fraction of the computing cost of the EnKF, but makes the crude assumption of no dynamical evolution of the errors. How do both these two methods compare in realistic settings of a Pacific Ocean forecasting system where the computational cost is a primary concern? In this paper the two methods are used to assimilate real altimetry data via a Hybrid Coordinate Ocean Model of the Pacific. The results are validated against the independent Argo temperature and salinity profiles and show that the EnKF has the advantage in terms of both temperature and salinity and in all parts of the domain, although not with a very striking difference. © 2010 American Meteorological Society.

Ren Z.-Y.,Shanghai JiaoTong University | Wang B.-L.,Shanghai JiaoTong University | Fan T.-T.,National Marine Environmental Forecasting Center | Liu H.,Shanghai JiaoTong University
Journal of Hydrodynamics | Year: 2013

On the 11th of March, 2011, a subduction earthquake of magnitude Mw9.0 happened at the northeast of Japan, generating a tsunami which resulted in huge damage in Japan. Okada's elastic fault model is used to generate the deformation of the sea bottom based on USGS sources and UCSB sources respectively. The shallow water equations are solved by the adaptively refined finite volume methods so that it can compute the propagation of tsunami in the Pacific Ocean efficiently. The computed time series of the surface elevation are compared with the measured data from NOAA real-time tsunami monitoring systems for model validation, and UCSB sources derive better results than USGS sources. Furthermore, one nested domain with fine grid and higher topography reso- lution is combined to compute numerically this tsunami spreading in the Bohai Sea, Yellow Sea, East China Sea, and North of South China Sea. The impacts on China Coast and seas are analyzed and discussed. The results show that the tsunami has almost no impact in the Bohai Sea and Yellow Sea. It has some kind impact on the East China Sea and South China Sea. However, maximum wave height on China Coast is smaller than 0.5 m. It is thus concluded that the 2011 Tohoku tsunami did not generate a significant in- fluence on China Coast. © 2013 Publishing House for Journal of Hydrodynamics.

Jiao Y.,Florida State University | Jiao Y.,National Marine Environmental Forecasting Center | Dewar W.K.,Florida State University
Journal of Physical Oceanography | Year: 2015

It has been shown recently that the California Undercurrent (CUC), and possibly poleward eastern boundary currents in general, generate mixing events through centrifugal instability (CI). Conditions favorable for CI are created by the strong horizontal shears developed in turbulent bottom layers of currents flowing in the direction of topographic waves. At points of abrupt topographic change, like promontories and capes, the coastal current separates from the boundary and injects gravitationally stable but dynamically unstable flow into the interior. The resulting finite-amplitude development of the instability involves overturnings and diabatic mixing. The purpose of this study is to examine the energetics of CI in order to characterize it as has been done for other instabilities and develop a framework in which to estimate its regional and global impacts. This study argues that CI is very efficient at mixing and possibly approaches what is thought to be the maximum efficiency for turbulent flows. The authors estimate that 10% of the initial energy in a CUC-like current is lost to either local mixing or the generation of unbalanced flows. The latter probably leads to nonlocal mixing. Thus, centrifugal instability is an effective process by which energy is lost from the balanced flow and spent in mixing neighboring water masses. The mixing is regionally important but of less global significance given its regional specificity. © 2015 American Meteorological Society.

Liu F.,CAS Institute of Atmospheric Physics | Liu F.,University of Hawaii at Manoa | Huang G.,CAS Institute of Atmospheric Physics | Feng L.,National Marine Environmental Forecasting Center
Theoretical and Applied Climatology | Year: 2012

To understand the nature and role of multi-scale interaction involved in the Madden-Julian oscillation (MJO), a dynamical model is built based on two essential processes: the convective complex of the MJO modulates the strength and location of synoptic-scale motions, which in turn feed back to the MJO through the convective momentum transfer (CMT). Our results exhibit that: (1) The lower tropospheric easterly CMT coming from the 2-day waves slows down the MJO dramatically; (2) although the lower tropospheric westerly CMT coming from the superclusters can produce the horizontal quadrupole vortex and vertical westerly wind-burst structures of the MJO, it drives the large-scale motions to propagate eastward too fast; (3) the planetary boundary layer provides an instability source for the MJO and pulls the MJO to propagate eastward at a speed of 0~10 ms -1; and (4) the optimal structure of the multi-scale MJO should be: the stronger superclusters/2-day waves prevail in the rear/front part of the MJO and produce lower tropospheric westerly/easterly CMT there. These theoretical results emphasize the role of CMT and encourage further observations in the multi-scale MJO. © 2011 Springer-Verlag.

Lin B.,National Marine Environmental Forecasting Center
Applied Mechanics and Materials | Year: 2014

This paper analyzes the advantages and disadvantages of cluster management system of B/S mode, combined with the need of practical application, puts forward the cluster management system structure of Browser/Server/Severs structure with a novel B/S model. This structure can achieve most of the functions of cluster management, and the advanced architecture, solves the problems of cluster management system for two or three layers of C/S structure. From the implementation point of view, this structure can greatly improve development efficiency, reduce development complexity. © (2014) Trans Tech Publications, Switzerland.

Lin B.,National Marine Environmental Forecasting Center
Lecture Notes in Electrical Engineering | Year: 2013

Tropical storm surge is one of the primary and also the most serious maritime disasters in the coastal areas of China. The backward aid decision supporting method is the largest and also the most urgent problem that is difficult to be solved in the current emergency management of tropical storm surge disaster prevention and reduction. In this paper, by applying the theory and technology of artificial intelligence (AI), researching knowledge base and reasoning machine, and using the rule-based production knowledge representation, the credibility-based forward reasoning strategy and the data-mining-based intelligent learning way, a practical AI is designed for tropical storm surge disaster prevention and reduction. © 2013 Springer-Verlag.

Li Y.,CAS Research Center for Eco Environmental Sciences | Geng D.,CAS Research Center for Eco Environmental Sciences | Geng D.,China University of Geosciences | Liu F.,National Marine Environmental Forecasting Center | And 4 more authors.
Atmospheric Environment | Year: 2012

Polyurethane foam (PUF)-disk based passive air samplers were deployed in King George Island, Antarctica, during the austral summer of 2009-2010, to investigate levels, distributions and potential sources of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in Antarctic air. The atmospheric levels of ∑ indicator PCBs and ∑ 14 PBDEs ranged from 1.66 to 6.50 pg m -3 and from 0.67 to 2.98 pg m -3, respectively. PCBs homologue profiles were dominated by di-PCBs, tri-PCBs and tetra-PCBs, whereas BDE-17 and BDE-28 were the predominant congeners of PBDEs, which could be explained by long-range atmospheric transport processes. However, the sampling sites close to the Antarctic research stations showed higher atmospheric concentrations of PCBs and PBDEs than the other sites, reflecting potential local sources from the Antarctic research stations. The non-Aroclor congener PCB-11 was found in all the air samples, with air concentrations of 3.60-31.4 pg m -3 (average 15.2 pg m -3). Comparison between the results derived from PUF-disk passive air sampling and high-volume air sampling validates the feasibility of using the passive air samplers in Antarctic air. To our knowledge, this study is the first employment of PUF-disk based passive air samplers in Antarctic atmosphere. © 2012 Elsevier Ltd.

Hou J.,Capital Normal University | Hou J.,National Marine Environmental Forecasting Center
International Conference on Geoinformatics | Year: 2016

In this paper, the spatial distribution of shipping routes is given after analyzing the global shipping routes with the methods of GIS analysis. The historical development and change of the global shipping routes are revealed with the combination of historical data. The analysis result shows that: The shipping routes among North America, Europe, and Asia constitute the main body of the global shipping routes. There are a number of key shipping routes in the global shipping routes, whose frequency of navigation is significantly higher than other routes. By comparing shipping routes of the 19th century with the ones in present day, we can see the key areas evolution of the global maritime transport from 'Europe-America-Africa' to 'Europe-North America-Asia'. The three most concentrated areas of ports in the world are Europe, North America, and East Asia. Asian ports, especially China's ports, have shown a very fast growth rate in the past forty years. © 2015 IEEE.

Lin B.,National Marine Environmental Forecasting Center
Applied Mechanics and Materials | Year: 2014

According to the guideline and target requirements of green ship engineering and the needs on the prevention and countermeasures of all kinds of natural disasters in ocean ships, a design scheme of the comprehensive information platform for the prevention of natural disasters based on ocean ships is proposed by the author in this paper. In this design scheme, the seamless time-space integration of heterogeneous information resources in different application systems is realized through using modern technologies such as computer technology, wireless communication technology, natural disasters forecast (alerting) technology, digital information integration processing technology, geographic information system (GIS), and global positioning system (GPS), and also higher-level information services are provided for the commanders (decision makers) of ocean ships in an integrated and unified way, thus promoting the self-security ability, distress searching and rescue aid decision-making ability, and the sea (especially ocean) transport and production operation abilities of ocean ships to be effectively increased. Besides, the re-optimization idea and improvement technology for the design scheme in the future allowable conditions, the unique information transmission technology (satellite communication technology) of the prevention of natural disasters in ocean ship, and the good development prospects of green ships are generally introduced and forecasted in this paper. © (2014) Trans Tech Publications, Switzerland.

Liu F.,University of Hawaii at Manoa | Huang G.,CAS Institute of Atmospheric Physics | Feng L.,National Marine Environmental Forecasting Center
Theoretical and Applied Climatology | Year: 2011

In observations, the 2-day waves, identified as the convectively coupled equatorial inertio-gravity (IG) waves, only propagate westward. To understand this feature, a simple theoretical model is presented for the convectively coupled equatorial waves (CCEWs). Under the assumption that the convective heating is proportional to the vertical velocity on the first baroclinic mode, the nonlinear governing equation for the meridional velocity of the CCEWs can be derived. The optimal method is used to obtain the dispersion relation from this nonlinear equation, and the results show that the deep convection can slow down the IG waves by decreasing the mean state static stability, but the key leading to the westward propagation of the IG waves is the full meridional variation of the sea surface temperature (SST). The warm SST trapped near the equator excites long westward propagating IG waves, whereas the warm SST trapped near the ITCZ centered at 10° N excites short westward propagating IG waves. This theoretical model provides a simple tool to study the CCEWs in understanding the tropical circulation. © 2011 Springer-Verlag.

Loading National Marine Environmental Forecasting Center collaborators
Loading National Marine Environmental Forecasting Center collaborators